An Early Look at the 2010 Urban Mobility Report: "Change" is Improving the Information

The Urban Mobility Report is a project of the Texas Transportation Institute (TTI) that provides several measures of regional traffic congestion problems. Because of its collaboration with INRIX, TTI was able to incorporate more roads and cities, and even more up-to-date congestion data, into the 2010 report. The 20th edition of the Urban Mobility Report has a new feature, the Commuter Stress Index (CSI), which is designed to replicate the experiences of commuters through congested thoroughfares. The CSI compares travel time per mile during peak to free-flow periods using only the most congested direction in each peak period; this shows the conditions that commuters traveling in predominant conditions (for example, inbound in the morning and outbound in the afternoon) actually experience. Delay and congestion cost were found to be different in most urban areas than with the old estimation procedure. The differences are not in the same direction; some regions have more delay, and others have less. For 2010, the "best available data" are much better than in past reports, and the procedures and estimates have been adapted to take advantage of those improvements. It appears that several factors cause estimated traffic speeds to be different than actual speeds: 1. Speeds on many congested sections of road are not as bad as previously estimated. There are severe bottlenecks with very low speeds, but most sections are not congested for more than four to five hours each day. 2. The true effects of incidents are not as significant as previously estimated. When crashes occur, congestion increases, but in most cases not as much as in previous estimates. The bottleneck delay that crashes cause is partially offset by free-flowing traffic once the crash scene has been passed. 3. Off-peak direction delay is not a significant problem on most roads. High daily traffic volumes were previously estimated to create travel delay in the "minor" direction. The real speeds indicate the congested time may be only half as much as previously estimated. Just as technology has helped mapmakers create more accurate and more detailed maps in the past several centuries, directly measured traffic speeds from mobile device and navigation technologies are helping TTI create a more accurate, detailed, and up-to-date report of traffic congestion and its effects.